Table of Contents
What is smallpox?
Smallpox is a highly infectious disease caused by the smallpox virus known as Variola virus; this infection has a mortality rate of more than 30% – this means that if 100 people get infected, more than 30 will die of the disease. Smallpox has no treatment but there is an effective smallpox vaccine that was used to eradicate Smallpox. It is the only infectious disease to have been eradicated.
The last case of smallpox was in Somalia in the year 1977 and smallpox was declared eradicated in 1980 after WHO vaccination campaign. Because universal vaccination against smallpox was stopped in the early 1970s, it has left the vast majority of the worlds population unprotected against the variola virus. Since the eradication of smallpox, populations of the virus have been preserved in 2 secure laboratories in Russia and USA. Edward Jenner developed a vaccine for smallpox in 1798.
What causes Smallpox? (Smallpox Causes)
The name of the virus that causes smallpox is called Variola virus. There are two types of variola virus: variola major and variola minor. The variola major being more severe and common.
How is smallpox spread? (Smallpox Transmission)
Smallpox is transmitted by inhaling droplets of the virus in air. It is an airborne disease. The patient having smallpox is infectious about 12 to 24 hours before the appearance of the smallpox rash this makes it possible to pass the infection to others before being recognized as suffering from smallpox.
Smallpox Symptoms and Signs
- High fever
- Red skin rashes containing a transparent fluid appear all over the body. The red spots then become filled with thick pus. The Skin rashes all develop together through the same stages having same sizes and shapes. The rashes first appear on the mucosa of the mouth and pharynx, face, and forearms and later spreads to the trunk and legs and becomes vesicular and later pustular.
- Eyelids become swollen and may become glued together.
- Recovery often leaves the sufferers with complications such as permanent blindness and disfigured by scabs that form when the pustules dried out
Smallpox incubation period
Smallpox has an incubation period of about 12 days which makes it difficult to know the initial source of infection.
Smallpox virus structure
The smallpox virus is a DNA virus belonging to a family of viruses known as Poxviridae this family is different from that of Chicken pox, hence smallpox is not the same as Chickenpox (this belongs to the Herpesviridae family and it is caused by a virus called Varicella-zoster).
The variola virus structure will be used to describe the morphology of the poxviridae family of viruses. The structure of the smallpox virus is the most complex of all known viruses. It looks like a brick-shaped box and has at its center a large complex DNA genome that helps the virus to code proteins. The DNA of smallpox virus is organized into a dumbbell shape with structural proteins that are surrounded by two envelopes. The smallpox virus carries many of its enzymes and this helps it to replicate in the cytoplasm.
Smallpox Laboratory tests for Diagnosis
- Use of Electron microscope to identify the vesicle or pustule content
- Use of culture to isolate the smallpox virus involved
- Serological tests
The name of smallpox vaccine is called Vaccinia vaccine it was developed using the vaccinia virus, which is not a virulent virus of the poxviridae family but it can induce immunity to prevent infection by the virulent poxviridae viruses such as the variola major virus that causes smallpox.
The smallpox vaccine was freeze-dried and could be kept at high temperatures for as long as six months this made the vaccine suitable for use in the tropics. Vaccination against smallpox is now recommended except for laboratory personnel handling certain poxviruses for experimental purposes.
Smallpox Eradication Programme
The World Health Organization (WHO) started the smallpox eradication programme in 1956 and there were two main aspects oftheprogramme: vaccination and surveillance. Whenever a case of smallpox was reported, everyone inthe household and the 30 surrounding households, aswell as other relatives and possible contacts in the area will be vaccinated this is known as ring vaccination and helps to protect everyone who could possibly have come into contact with a person with the disease. The last places with cases of smallpox were in East Africa, Afghanistan and the Indian subcontinent. Eradication was most difficult in Ethiopia and Somalia because many people lived in remote districts well away from town and accessibility was difficult.